PREPARATIONS: Tablets: 250mg; 500mg. Oral suspension: 100 mg/mL; 125 mg/5mL; 250 mg/5mL.
STORAGE: Tablets should be kept between 15°C (59°F) and 30°C (86°F). The solution should be kept refrigerated, and can be used for up to 14 days after it is reconstituted by the pharmacist. It must be shaken before each use and should be kept well sealed.
PRESCRIBED FOR: Oral ampicillin (or amoxicillin) is effective against susceptible bacteria causing infections of the middle ear, sinuses, bladder, and kidney. Only mild to moderate infections are treated with oral ampicillin. Bacteria against which ampicillin often is effective include: enterococci, Listeria monocytogenes, Neisseria gonorrhoeae, Neisseria meningitidis, some Hemophilus influenzae, Gardnerella vaginalis, Bordetella pertussis, and some E. coli, Proteus mirabilis, Salmonella, and Shigella. Susceptibilities of bacteria to antibiotics vary from location to location. Thus, some doctors may use ampicillin or amoxicillin first for some infections, whereas other doctors may use more "broad-spectrum" antibiotics.
DOSING: Food in the stomach reduces how much and how quickly ampicillin is absorbed. Administration should be either 1 hour prior to or 2 hours following a meal for maximal absorption. However, for persons who experience nausea or stomach distress after taking ampicillin, it may be taken with meals. Ampicillin most often is given four times a day for 7 to 14 days. When used to treat gonorrhea, it is given as a single large dose (for example, seven 500mg capsules) with probenecid. The probenecid slows down the elimination of the ampicillin so that the ampicillin remains in the body longer.
DRUG INTERACTIONS: Probenecid (Benemid), causes an increase in the amount of ampicillin in the body. This interaction may be used to advantage. (See Dosing.) Use of ampicillin with allopurinol can increase the incidence of drug-related skin rash. Very high doses of ampicillin (at least 1 gram or 1000 mg) can decrease the effect of atenolol (Tenormin) by decreasing its concentration in the blood. Similarly, ampicillin, even in normal doses, can decrease the effectiveness of birth control pills by decreasing the blood concentrations of the estrogens in the birth control pills.
PREGNANCY: Ampicillin is considered safe during pregnancy.
NURSING MOTHERS: Ampicillin is excreted in breast milk. No side effects have been reported in nursing infants whose mothers have taken ampicillin. Concern for side effects such as allergic reactions, of course, exist. Thus, physicians weigh the potential risk of allergy versus the benefits.
SIDE EFFECTS: Allergic reactions are relatively common side effects during therapy with any of the penicillins. These reactions can range from rashes to anaphylaxis, a severe condition in which there may be shock and even death. Rashes occur more frequently with ampicillin than with the other penicillins. The incidence of rash with ampicillin seems to be higher in patients with viral illnesses, such as mononucleosis. Patients with a history of allergic reaction to any other penicillin should not receive ampicillin. Persons who are allergic to the cephalosporin class of antibiotics which is more distantly related to the penicillins (e.g., Ceclor, Keflex, Cefzil) may or may not be allergic to penicillins.
Nausea, vomiting, loss of appetite, diarrhea, and abdominal pain are commonly reported gastrointestinal side effects during ampicillin therapy, but are rarely severe. Diarrhea appears to occur more frequently with ampicillin than with the other penicillins.
